HTML5 Video is coming to Opera 10.5. Yesterday (or technically, last year--happy new year readers!) Opera released a new alpha build containing a preview of their HTML5 Video support. There's a number of details to note, not least that this is still an early alpha...

You keep posting wrong things about WebKit over and over again.
As proof for your accusations, you post links to an article, that merely states the varying degrees of WebKit port quality on different platforms.
I don't know if you don't know better of if you're lying on purpose.
No matter what, here are some facts:

Fact 1:
WebKit is not controlled by Apple.
Apple initiated WebKit and provides the hosting infrastructure. Other than that Apple has no special role in WebKit these days. Apple engineers work together with Google, GNONE, and Nokia ones.
They all have equal rights.
Anyone who reads http://webkit.org/blog/ sees postings about new source code reviewers (with full commit rights) quite regularly.

Fact 3:
Quality varies from port to port.
When a vendor releases a browser based on WebKit, it works like this: the main trunk is branched and the vendor focuses his work (bug fixing) on that branch. That's the same for every vendor. Newer ports or branches by smaller vendors may not get as much bug fixing as e.g. the Chrome port by Google.
There may also be bugs in the used toolkit. Those bugs are out of scope to fix for the WebKit project.
Branches are made on a regular basis from the main trunk. A branch does not serve as primary development place for a port.
All big software projects use the trunk/branch development model. It's a proven model and does not equal unmanageable forks.

Fact 4:
Rendering capabilities depend on the graphics library.
WebKit does not have a single, unified graphics library. Gecko for example uses Cairo. Opera uses something proprietary.
If a vendor decides to port WebKit to a new graphics library instead of adapting the graphics library to the platform, regressions may occur.
No vendor is forced to port WebKit to a new graphics library. WebKit has already been ported to Cairo. If a vendor wants to improve on that one, he is free to do so.
Still, most vendors prefer porting to new/native graphics libraries. This reduces memory footprint -- especially important in mobile space. Vendors may see this as more important than 100% compatibility with existing ports.

You keep thinking that things work in the real world as they do in rosy-red theory land.

Fact 1: Apple does control the project in practice. Even if this changes, Webkit will still only be controlled by a couple of major contributors, most likely Google and Apple. Despite Nokia's size, they ended up with a broken fork, and had to start from scratch. For smaller players, Webkit will never be within their control. When even Nokia can't pull it off, how would others be able to?

Fact 2: You end up with forks in practice. Look at Nokia again.

Fact 3: Not only does the quality vary depending on the port, but each port will eventually either have to become fully forked, or work will have to be thrown away to be aligned with the main Webkit project, which is run by at most a couple of major players. Right now, Apple is basically the owner.

Fact 4: Indeed, there is more to a browser than the browser engine. Webkit is a not at all easy to work with, and when you start integrating with platforms, creating your own UI, etc. you quickly end up with a separate and incompatible fork.

So as you can see, Webkit is no easy solution. It's hard, requires a lot of work, and unless you are a giant like Google or Apple, you will forever be at the mercy of the Webkit "owners".